Flexible sheeted abrasive



Patented Mar. 23, 1943 FLExIBLEs'HnETEn AnaAsrvE i Durward Ogden Guth,StPaul, assignmto Minnesota Mining & Manufacturing. Company, St. Paul,Minn., a corporation of Minna sota No Drawing. Application March, 1929,Serial No. 347,159 I 5 Claims. (o i n-29s The present invention relatesin general'to'a treatment of material, preferably in sheet form, andmore'particularly to the treatment of material forthe purpose ofobtaining or forming composite structures of which forms of abrasivesuch as what is commonly known as sandpaper is an example.

Although I hereinafter disclose the practice of my inventionin'connection with abrasives such as sandpaper, it will be understoodthat my invention of certain features thereof has a wider field ofutility; I, V g

Composite structures'qof the abrasive type, such as sand-paper or emerycloth, comprises generally (a) a ,b'asewf sheet materialwhich may befelted a's'in the case of paperor woven as in the'case of cloth; (b) amore or less finely comminuted reslstant'material having abradi lDroperties such as. garnet or corundum and (c) a. binder generally inthe form of gluewhich serves tobind-the abrasive to the base.

products suitable for liquid sanding operations terials of the resinoustype or resin-varnish type including drying oils, the raw materialsbeing of extremely complex, arbitrary nature or having varyingproperties due to the methods used for their production, derivation orextraction from their natural sources, these materials have been Where Ihave attempted to make abrasiveof application to the materials enteringinto an abrasive article,'such as the base or backing, either cloth orpaper, and'the abrasive grit or layer, ,whether of the natural,electro-furnace type, vitreous type or baked type abrasive and assureuniformity of results so far as the weight of the articleis concerned,its deterioration fac- ;tor throughout periods of storage, flexibilityand found to give non-uniform results or results whose uniformity canonly be controlled by exercising a high order of care. sive articles,particularly materials of this character when spread in thin films orabsorbed in porous backing materials such as paper or spread uponabrasive particles, have such a high order of surface exposure thatatmospheric conditions, temperature changes, oxidation and actiniceffects tend to deteriorate the material beyond a desired degree withoutcontrol. The preliminary preparation of an abrasive material of theresinous or drying oiltype above referred to is of such complexcharacter that when used with thinners orsolvents therefor to saturate,impregnate or otherwise coat the base or backing, uniformity is not acertainty and such factors as porosity of paper, ability to wet theabrasive due to the nature of its surface, etc., will give markednonuniform results in the final product. i

The present invention contemplates the pro-. vision of an abrasivearticle in the nature of sandpaper and a 'new binding materialsusceptible In, sheeted abra-.

resistance to mechanical agencies when used in dry or wet abradingoperations and which'properties may be obtained with great facility,without special care and permits the utilization of standard equipmentin the abrasive art, such as sandpaper.

In its preferred form, vrr'iy'invention contemplates the provision of anabrasive articleiin the nature of sandpaper including the reaction,condensation or polymerization of products resulting when polyhyd-ricalcohols or their anhydrides or similar compounds or when polyhydricacids or,

their anhydrides or similar compounds are used as components, togetherwith another compound or compounds, with or without a modifying agent oragents to produce such'compounds' as commonly are called syntheticresins or comdensation products and one which functions more efii-iciently than any other prior binder known to me; the provision of anabrasive article having a binder characterized by its uniformity ofphysical andchemical properties whereby any desired and predetermineddegree of flexibility may be impartedto theabrasive article; theprovision of an abrasive article having, a binder characterized byextensibility and compressibility to accommodate itself to flexion ofthe base without permanent distortion, deleterious distinteg ration dueto'atmospheric conditions, temperature changes or actinio exposure; theprovisions of an abrasive article having a binder'of great tensilestrength and flexibility resulting from the ability of the binder totenaciously attach itself to materials of various surfacecharacteristics, such as natural or artificial abrasive particles andthe porous base or backing and obtain uniformity of the compositearticle as to flexibility, abrasive resistance,

and which may be conducted with an exercise of a low order of care; theprovision of an abrasive article having a binder which is resistant toliquids used in sanding operations or finishing,

operations, whether water, organic solvents orinorganic materials, suchass'trong acids or alkalis;

the provision of an abrasive article having a binder which may beattached to an organic base or backing material, such as paper and whichmay be further matured to its final stage without impairing the physicalproperties of the base or backing and which maturing process may beexpedited beyond the speed heretofore practicable;

of an abrasive article including a binder which;

may be used in any pointin the compositestructure of the abrasivearticle such as the size, back size or pre-size and a bond and sand orgrit size,

as best to attain the desired ends, viewed from certain aspects.

In carrrying out my invention, in order that the resinous material maybe of a known quantity and of known quality, and of predetermined ageingproperties, I prefer to react, condense or polymerize polyhydricalcohols or their anhydrides or similar compounds or polyhydric acids ortheir anhydrides or similar compounds, used as components, together, orwith another compound or compounds, with which they are adapted toreact, condense or polymerize to resinify, and may be further suitably,modified by agents to impart additional properties of flexibility andpenetrability of the base or backing or for adhesively binding thevarious abrasive without material modification of the binder for thevarious purposes enumerated.

In the employment of my present invention for the production ofsandpaper and the like (which I cite for purposes of example) I use asthe base such a sheet of material (a woven web of material or adeposited or felted web of material such as paper) as will havepredetermined porosity factors and serve conveniently for the employmentcontemplated, and as the abrasive I use such comminuted material as maybe classified as natural abrasives, such a flint, garnet or corundum, orartificial abrasives such as of the character used for makingargillaceous refractories or electro-fumace products, as silicon carbideor the like of various grades and sizes, surface character, etc., as issimilarly adapted to perform the function in view.

It is most desirable that the binder utilized have the functions andcharacteristics not only of great mechanical strength, includingtoughness, resistance to tensile and shearing strains and of greatbinding strength, including adhesiveness and tenacity and ability to wetabrasive particles under all conditions '01 surface contour, but alsothat it be moisture resistant, unaffected by a large number of liquidswhich may be used in liquid sanding operations, easily worked, made ofmaterials easily obtainable on the market, of definite chemicalcomposition and uniformity, inexpensively and facilely worked andapplied and. when used with a. base material which is penetrable,penetrative of such base as to form a strong union therewith and,furthermore, when built up into a plural layered composite article,retain a predetermined flexibility, free from deteriorating factors suchas changes in temperature, atmospheric conditions or actinic exposure.

I have discovered that resinous materials including a polyhydricsubstance are preferable not only to gum, gum resins, hardened oils, butto phenolic condensation products for purposes contemplated by me, andparticularly resins having as their base polyhydric substances or theiranhydrides, which are peculiarly adapted for my ends for a number ofreasons, including that their characteristics can not only be bettercontrolled than in the case of the other materials first enumerated,-but that batches of the desired characteristics can be readilyreduplicated and the desired properties imparted to the compositeartlcle with a large variation in the basic ingredi ents, such as thebacking and the abrasive particles, I'have found that certain materials,such as polyhydrlc alcohols orpolyhydric acids are available to give byinteractions, condensation or polymerization a material which ispreferred by me as a major constituent of the binder, that is,

particles. The treatment to which I subjedt these basic materialsresults in a resinified comppsition, in certain aspects possessingnovelty, uniformity and physical properties peculiarly useful in thesheeted abrasive art, such as freedom from gumminess or tendency to clogduring intensive abrasive operations.

In producing the desired binder, I employ "a number of alternativemethods, each of which appears to have certain favorable characteristicsand advantages. One method which has given very good results will now bedescribed in some detail as Example I 100 g. of polyglycerine 200 g.phthalic anhydride are mixed together and held for a short time at atemperature of 100 to 110 be heated for direct application to form asize or bond on thinned for sizing. This material may be used as a papersize, sandize, backsize, a binder or bond for the abrasive particles.The

consistency may be modified to take care of such components as porosityand penetrativeness of the backsize. For instance, with paper having alow porosity and high penetrative properties I may heat the resin foronly thirty minutes at 110 C. and use 35%. thinners of such a nature as50% benzol and 50% acetone together with 65% resin. On the other hand,for a paper having a high porosity and low penetrativ properties I mayheat the. resin for, say, three hours at 110 C. and use 45% thinners and55% resin for produ'cing pre-size. It is evident from this that byvarying the quantity of condensation and/or polymerization of the resinand varying the quantity of thinners I may be able to takecare of suchfactors as porosity and penetrativeness of the base. After separation ofthe solvent, if such is used, the resin may be matured by heat ing at atemperature of from to C. for a period of 19 hours or where the materialis applied in fairly thin layers, a higher temperature for a shorterperiod of time may be utilized to set the final product.

In this type of resin particularly, this condensation resin may becombined with modifying agents such as various drying, semi-drying andnon-drying oils. Though the example has been given with phthalicanhydride as the single aromatic acid, this may be combined with analiphatic acid, such as oleic, butyric, succinic,

citric, benzoic, malic, glutaric, suberic, camphoric,

adipic, lineoleic and eleostearic and others.

Though I have mentioned above polyglycerine as the polyhydric compound,under some condi-v C. The resulting product will produce a resinous masswhich may tions, though not as preferable, glycol and other polyhydricalcohols may be used, such as 1-2 dihydroxyethane 1-2 dihydroxypropane1-3 dihydroxypropane 1-2-3 trihydroxypropane Under certain otherconditions those materials which areclosely analogous to carbohydrates,in-

cluding such materials as sugars, starches, cellu- V I I 100 got theresin as produced in Example I g'. of China-wood oil are mixed: and heldat a temperature of about 110 C. for about 5 minutes, with continuedstirring. This resinous material may now be thinned in accordance withthe proportions enumerated above to vary the consistency of the solutionto takecare of the porosity of the base orbacking and the size andcharacter of the abrasive particles. After evaporation of the vehicle orsolvent, the base with its residue may be heated to mature the sametemperatures from 85 C. to 90 C. for a other oils which may be used arethe various dryfor amaterial having a low porosity and low period ofabout 19 hours. In the example given,

ing, semi-drying and non-drying oils, such as wood oil, linseed oil,castor oil, cottonseed oil, ra'pe seed oil and soya bean oil, withinlimits approxiilcation as to the quantity depending upon' the base orbacking. These oils or'modifying' agents Gelatinizing substances, suchas camphor substitutes and theheavier, less volatile solvents for theresins may also be included. Of the gelatinizing agents and high boilingsolvents, there may be used the gelatinizing agents or solvents used inconnection with cellulosic compounds,"such as nitro cellulose, celluloseethers and esters." The camphor'substitutesor gelatinizing agentsreferred to are particularly desirable in that they are volatile, whichleave the binder or resinous base free from gumminess tending toaccumulate 'mating 15% to 50% of the resin, with the modi-' 35 act inthe nature of softening agents or emollients. 40

and clog the sandpaper by the abradedparticles removed in the abradingoperations. 7 i

The previous examples produce materials which are usually to bepreferred as a binder, sandsize or backsize. I have found it possible toproduce =9; material admirably adapted for a paper treatment or centersizeby the following example:

Example III 100 g. diethyleneglycol 200 g. phthalic anhydride and 50%alcohol in proportions of 35% resin and 70 solvents, This material m'aybe used as a centerslze or presize for paper. The paper may or may notbe subjected to abaking treatment afterward. For'certain purposes thisresin may desirable properties to the cellulose ester, and-in turnreceiving desirable properties'froniv it.

i The binder whether for forming a size, an abrasive bond or sandsize,does not necessarily include a polyhydric acid or its anhydride. Anexampleof a preparation in which-only one of-the constituents ispolyhydric is given as follows:

Example IV 100 g. of phenol I g. of glycerol 7 V2 8. of concentratedsulfuric acid.

are refluxedat a temperature between 160 and.

190 C. until 35 g. of water have been distilled carbonate. Any otherbasic material, such as, for instance, hydroxides, carbonates or similarcompounds 01' the alkali metals or alkali earths, are suitable. Calciumoxide may further be mentioned as another suitable neutralizing agent.'I'hismaterial maybe usedas a paper size, sandsize; backsize, a binderor' bond for abrasive particles. The consistency may be modified to takecare of such components as porosity and penetrativeness of the base andbacking. For instance,

penetrative properties I may distill oil only 32 g. of water and use 35%thinners such as benzol together with 65% resin for the production of apresize: while for a paper having a high porosity and high penetrativeproperties I may distill off 37 g. of water and use 45% thinners and 55%resin for producing the same action as a presize. I may use as solventsfor this type of resin such solvents as acetone, alcohol, amyl-acetateor Cellosolve or mixtures of these solvents.

To produce a binder, the solutions of a resin above referred to may bemodifledso that 35% to 15% of solvents may be added to 65% to 85% ofresin-instead of the percentages of'solventof a higher order which arereferred to above. These percentages may-be varied as well as thesolvent to take care of the size of fineness of the grit and itscharacter. Thus, using garnet as the abrasive, of a fineness of 280, thepreferred proportions of resin to solvent are to 25, in which thesolvent is preferably 25. With a coarser abrasive having a fineness of'220 mesh, I may use a binder mixture having resin solvent 20%. Undercertain conditions it will be observed that the resinous material maybemade to partial completeness and of a fluidity sufllcient to be usedas a bond or penetrative sizing coat directly.

Where the resinous material as above described, with or without thesolvent is used for a fabric size or a bond or sand size, itispreferable to set the resinous residue by heat or, where a solvent orthinner has been used, to apply the resinous material, these solventsmay be recovered 'by suitablerecovery apparatus. The resinous material;whether applied with a thlnneror directly, is matured by heat inaccordance with the desired flexibility, hardness and insolubility invarious solvents. The'hlgher the temperature, the more infusible andinsoluble will be the flnal product for a given time of baking. Also,with the higher temperatures, a change to the final product takes placemore readily. With a mixture as above described in Example I, atemperature from 80 to C. for 15 hours will produce a change to thefinal stage of high infusibility;

V a temperature from to 200 C.---for 5 to 10 hours will procureapproximately the same result.

be dissolved in a-celluiose ester solution imparting 75 However, wherethe resinous material'is applied over. The sulfuric acid is neutralizedwith barium in relatively thin layers and a highly bibulous type ofpaper is used, for purposes of preventing scorching of the paper and byreason of the thinness of the layer of resinous material, a hightemperature may be used to quickly mature the resin to the final stagewithout scorching the paper. Certain additional flexibility may beimparted to the resinous material by the addition of various oils,amongst which there may be enumerated wood oil, linseed oil, castor oil,cottonseed oil, rape seed oil, soya bean oil, as well as othersemi-drying and non-drying oils. These may be added in proportions asfollows:

' Per cent Final resin 80 Oil 20 A modification of Example I may bepracticed as follows:

Example V 100 g. of glycerine 200 g. of phthalic anhydride are heated toabout 185 C. until the evolution of water has ceased. This product ismixed with about 150 g. of. China-wood oil and heated in contact with adispersing agent, of which benzyl benzoate about 500 g. may be cited asexample, to about 200 C. Upon-removal of the dispersion agent byprecipitation with benzol, the remain-'- ing product is admirablysuitable for the uses described in connection with the Examples I andII, where solution is aifected by solvents such as ethyl alcohol andbenzene in proportions of 50% of alcohol to 50% of benzene. Otherdispersion agents may be usedas follows: benzyl acetate, nitrobenzene,toluidine, benzyl alcohol, cresol, aniline, glycol diacetate,phenol-hydrazine and orthocresol benzoate. This material may be thinnedto the consistency for producing best results for penetration of a.porous base or backing, such as paper, and for wetting and tena ciouslybinding abrasive particles, depending upon the fineness and size of theabrasive particles and their general surface condition, due to itsinherent characteristics.

For'a paper of the character previously described in Examples I and II,I may thin the resin above described with about 30% of a solvent such as50% alcohol and 50% benzene. After removal of the solvent, this resinmay be matured or set by heat at a temperature of from 80 to 100 C. fora period of 19 hours. A higher temperature and a lower time of exposuremay be utilized where the resinous material is spread in very thinlayers. As recited in the case of Examples I and II, the otherpolyhydric materials may be used with a certain amount of success. Also,the other aromatic acids or their anhydrides or mixtures of aromatic andaliphatic acids may be used.

I have also found that it is sometimes advantageous to use a resincomposed of constituents r as a catalyst.

. preceding methods.

with other' materials than those above enumerated and reacted alone withpolyhydric compounds. It is possible for me to produce resins havingdesirable properties in which only part of the constituents are apolyhydric resin. This may be done in several different ways. I mayreact together some of the constituents, after which I add the remainingconstituents to produce the final resin.

Example VI 200 g. phthalic anhydride g. glycerol are heated together at100 C. for one hour. The resultant resin is dissolved in 300 g. offurfural, after which 300 g. of cresol are added. 10 g. of an alcoholicsolution of hydrochloric acid serves as a catalyst for accelerating thehardening of this resin. This resin instead of requiring 20 hours toharden as is the case in Example IV. required about one-half as long, or10 hours in which to harden. This resin may be modified by variousproducts as outlined in Examples I and II to take care of porosity,penetrativeness or particle size.

Example VII This procedure will produce a slightly different resin byreacting together 200 g. of p'nthalic anhydride and 100 g. of glycerolas outlined in Example VI. To this I add 600 g. of a resin produced byheating 300 g. furfural 300 g; cresol with 10 g. of an alcoholsolution-of hydrochloric acid until the resin begins'to polymerize andbody at about the desired consistency. At this stage I add sufficientbase in the form of sodium hydroxide, barium hydroxide or similarcompound to neutralize the hydrochloric acid used These two resins Ithen mix together and use as outlined in Example VI.

I may, on the other hand, introduce all of the components at one time,reacting them together and produce a resin which is different in itsproperties from, that produced by either of the For instance:

Example VIII 200 g. phthalic anhydride 100 g. glycerol 200 g. furfural300 g. cresol 25 g. alcoholic solution of hydrochloric acid as catalyst.I heat this, mix until the desired body is produced, at which time I addsufficient quantity of base to neutralize all but 5 g. of the alcoholicsolution of hydrochloric acid. This resin may also be used in the samemanner as Example VI.

Although in Examples VI, VII, and VIII the proportions and constituentshave been kept- In the claims where I have referred to "vehicle freebinder, I mean to include thereby the resinifled binder without thesolvent, or vehicle, in accordance with the heretofore describedembodiments, in the nature of a vehicle or volatile I solvent.

Having thus'described my invention and illustrated its use, what I claimas new and desire to secure by Letters Patent is: v

1. The new article of manufacture in the nature of sandpaper comprisinga flexible sheet of fabric, a grit or layer of abrasive particles and awaterproof, stable adhesive bond including a condensation product ofphenol and a polyhydric alcohol interposed between saidigrit and saidsheet and of a nature to adequately maintain its bonding eifect insubstantially full measure throughout the effective abrading life of theabrasive article, even under sustained application of, or immersion in,liquids used in abrading operations but not materially affecting theflexibility of said sheet when dry.

2. The new'article of manufacture in the nature of sandpaper comprisinga flexible sheet of fabric, a grit or layer of abrasive particles and awaterproof, stable adhesive bond including a condensation product ofphenol and glycerol interwaterproof, stable adhesive bond including aresmined condensation product of 100 gr. of phenol and 70 gr. ofglycerol matured at a temperature from 80 to 200 C. andinterposedbetween said grit and said sheet and of a nature to adequately maintainits bonding effect in substantially full measure throughout theeffective abradin life of the abrasive article, even under sustainedapplication of, or immersion in, liquids used in abrading operations butnot materially aifecting the flexibility of said sheet when dry.

4. The new article of manufacture in the nature of sandpaper comprisinga flexible sheet of fabric, a grit or layer of abrasive particles and awaterproof, stableadhesive bond including a condensation product ofphenol, a polyhydric alcohol and an oil interposed between said grit andsaid sheet and of anature to adequately maintain its posed between saidgrit and said sheet and of a l nature to adequately maintain its bondingeffect in substantially full measure throughout the effective abradinglife of the abrasive article, even under sustained application of, orimmersion in, liquids used'in abrading operations but not materiallyaffecting the flexibility of said sheet when dry.

3. The new article of manufacture in the nature of sandpaper comprisinga flexible sheet of fabric, a grit or layer of abrasive particles and abonding effect in substantially ,full measure throughout the effectiveabrading life of the abrasive article, even under sustained applicationof,'or immersion in, liquids used in abrading operations but notmaterially affecting the flexibilityof said sheet when'dry.

5. The new. article of manufacture in the nature of sandpaper comprisinga flexible sheet of fabric, a grit or layer of abrasive particles and awaterproof, stableadhesive bond including a condensation product ofphenol, a polyhydric alcohol and a softening agent interposed betweensaid-grit and said sheet and of anature to adequately maintain itsbonding effect in substantially full measure throughout the effectiveabrading life of the abrasive article, even under sustained applicationof), orimmersion in, liquids

